1. Field of the Invention
The present invention relates to a detection apparatus for road obstructions using an image and, more particularly, to a detection apparatus for road obstructions which is designed to make it possible to accurately decide road obstructions such as wave-overtopping in a road video taken by a road monitoring camera.
2. Description of the Related Art
Conventionally, an inter-frame difference method has been proposed as a method of automatically detecting obstruction occurrence or the like on a road from monitor video data. According to this method, a differential data between pixel values of a present frame and a previous frame of the monitor camera video data is formed, and the differential data is used to search for obstructions on the road. A technique of forming a differential data between pixel values of a present frame and a previous frame of video data and detecting a moving object by using the differential data is exactly described in, for example, “Image Processing Handbook” issued from SHOKODO Co., Ltd. pp. 375-376, 1987.
For example, in order to detect occurrence of wave-overtopping (tidal wave) on a coast road to perform alarming by using the conventional method, a running vehicle and wave-overtopping must be accurately discriminated from each other in a differential data. For this purpose, the white of a wave and the color of a vehicle must be discriminated from each other.
However, many cameras for monitoring roads are monochromatic cameras, color data is rarely obtained. In addition, brightnesses in morning, day, and evening are considerably different from each other. For this reason, the discrimination is made excessively depending on the brightnesses, erroneous detections may be performed in many cases. Furthermore, when a vehicle having a color which is the same as or is similar to that of a wave is running, the running of the vehicle is erroneously detected as wave-overtopping in many cases.